JPH09297221A - Surface light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source device excellent in the uniformity of light source light. SOLUTION: This device 1 is provided with a tubular light source 501, a light transmission plate 101 introducing the light from the light source 501 and including a light introducing surface arranged proximately to the light source 501, and a control means arranged on one principal surface 131a of the plate 101 and controlling the peak of the light source light outgoing from the plate 101. The light from the light source 501 is made incident only on one principal surface 121a corresponding to the light source 501 which is set as the light introducing surface of the plate 101.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an edge light type surface light source device.

[0002]

2. Description of the Related Art A display device represented by a liquid crystal display device is:
It has come to be used as various display devices for televisions, computers, car navigation systems, etc. by taking advantage of its features such as thinness, light weight, and low power consumption.

For example, a light transmission type liquid crystal display device includes a liquid crystal panel having a liquid crystal layer held between a pair of electrode substrates,
A surface light source device that is disposed on one main surface of the liquid crystal panel and guides light source light to the liquid crystal panel.

In such a display device, in order to further reduce the thickness and size of the device, it is necessary to achieve a reduction in the thickness of the surface light source device. It has become.

An edge light type surface light source device is, as disclosed in Japanese Utility Model Laid-Open No. 63-24529, a tubular light source and a thin plate shape such as an acrylic resin having a milky white scattering pattern printed on the back side. A light guide plate is included, and one end surface of the light guide plate is disposed in proximity to the tubular light source. Then, the light source light from the tubular light source propagates through the light guide plate, is scattered by the scattering pattern on the back surface of the light guide plate, and is emitted to the main surface of the light guide plate.

[0006]

According to the edge light type surface light source device described above, although the device can be made thinner, there is light loss due to the scattering pattern, and it is necessary to print the scattering pattern separately. Therefore, improvements in light use efficiency and productivity have been desired.

To solve the above-mentioned problems, for example, Japanese Patent Application Laid-Open Nos. Hei 5-313163 and Hei 6-751
An edge light type surface light source device disclosed in, for example, Japanese Patent No. 23 gazette is known. In this method, a plurality of protrusions are arranged on the main surface side of the light guide plate opposite to the display panel side, and the light emitted from the light guide plate is controlled by the protrusions. Light use efficiency can be improved.

Similarly, the present applicant arranges a plurality of projections on the main surface side of the light guide plate facing the display panel, and controls the light emitted from the light guide plate by these projections. Are proposed, and a surface light source device with improved light use efficiency is proposed.

The above surface light source device will be described with reference to FIG. This surface light source device (1001) has a substantially rectangular light guide plate (1101) made of acrylic, and one end surface (1121a) of the light guide plate (1101).
Is used as a light incident surface, and includes a tubular light source (1501) arranged in proximity to the end surface (1121a) and a prism sheet (1901) arranged on the light guide plate (1101). And the light guide plate (1101)
Includes a plurality of comb-teeth-shaped prism protrusion rows (1141) substantially parallel to the tube length direction of the tubular light source (1501).

The prism projection row (1141) is provided with a tubular light source (1).
501) a first slope (1143) that is inclined close to the pipe length direction;
A second slope (1145) intersecting with the first slope (1143),
The first slope (1143) intersects the main surface (1131) of the light guide plate (1101) at an angle (θ1), and the second slope (1145) intersects the light guide plate (1145).
It intersects with the main surface (1131) at an angle (θ2).

[0011] The light source light emitted from the tubular light source (1501) is based on the difference in refractive index between the air and the acrylic resin.
The light has a condensing angle (Ω1) of about 42 ° in (1101), and the angle (θ1) is set to the condition that the light source light propagating in the light guide plate (1101) is totally reflected. Is the light guide plate (110
1) It is set to the condition that the light source light propagating inside is emitted.

Thus, the first of the rows of prism projections (1141)
When the light source light is guided to the slope (1143), the light source light is directed to the first slope (1143).
143), is totally reflected, guided to the second slope (1145), which is the exit surface, passes through the second slope (1145), and passes through the main surface of the light guide plate (1101).
It is converged at a converging angle (Ω2) of about 90 ° with respect to (1131) and emitted as directional outgoing light. In addition, the light guide plate (1
The light is emitted through the light-condensing sheet (1901) so that the main surface (1131) of 101) has a luminance peak in a direction substantially normal to the main surface.

By the way, in the above-mentioned surface light source device (1001), several bright lines appear in the vicinity of the tubular light source (1501) substantially parallel to the tube length direction. For this reason, the region where the bright line appears cannot be used as an effective light emitting surface, so that there is a problem that the non-effective light emitting surface is increased as compared with the conventional surface light source device, and the size of the device is increased. The present invention has been made in consideration of the above technical problems, and an object thereof is to provide a surface light source device having excellent uniformity of light from a light source.

[0014]

According to a first aspect of the present invention, there is provided a tubular light source, and a light guide plate including a light introducing surface disposed near the tubular light source for introducing light source light from the tubular light source. In a surface light source device provided with a control means for controlling the peak of the light source light that is arranged on one main surface of the light guide plate and is expressed from the light guide plate, the light source light from the tubular light source is
In the surface light source device, only one main surface corresponding to the tubular light source is incident as the light introduction surface of the light guide plate.

The invention according to claim 2 is the surface light source device according to claim 1, wherein the one main surface of the light guide plate and the light introducing surface are substantially in contact with each other by a line. .
In the invention described in claim 3, a light incidence blocking layer for blocking the introduction of the light source light into the light guide plate is disposed in a boundary region between the one main surface of the light guide plate and the light introduction surface. It is in the surface light source device of Claim 1 characterized by the above-mentioned.

According to a fourth aspect of the present invention, the light guide plate is configured to selectively emit the light source light propagating in the light guide plate from the one main surface side of the light guide plate. The surface light source device according to claim 1, further comprising a plurality of protrusions arranged on one main surface.

According to a fifth aspect of the present invention, the control means controls the peak of the light source light selectively emitted from the one main surface of the light guide plate in a direction normal to the one main surface. It is in the surface light source device of Claim 4 characterized by the above-mentioned.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Before explaining the present invention, the reason why a bright line appears in a conventional surface light source device will be briefly described. In the conventional surface light source device (1001) shown in FIG. 4, when traced from the bright line, the light source light enters the light guide plate (1101) from other than the original light introduction surface, that is, the one end surface (1121a) of the light guide plate (1101). It turned out that it was incident. More specifically, as shown in FIG. 5, an abnormal surface (1123) mainly having an angle (θ3) of 40 to 50 °
It was understood that it was incident from.

The incident light from the extraordinary surface (1123) becomes light having a converging angle (Ω1) of about 42 ° in the light guide plate (1101) due to the difference in refractive index between air and acrylic resin. Light guide plate
Propagate in (1101). Then, the main surface of the light guide plate (1101) (1
If the angle formed with 131) exceeds the predetermined range, it will be expressed as extraordinary light, and this will be the bright line. In addition, the abnormal surface (1123
The light source incident from the normal direction to a) is 93%.
The intense extraordinary light is introduced into the light guide plate (1101) with a high transmittance, is reflected by the main surface (1131) of the light guide plate (1101), and propagates in the light guide plate (1101). However, when the above-mentioned strong extraordinary light is reflected, depending on the surface state of the main surface (1131) of the light guide plate (1101), some of the extraordinary light is emitted from the light guide plate (1101) and also has a different reflection angle. It is thought that this causes several bright lines.

Here, only the lower end surface of the light guide plate (1101) has been described, but it was also found that the same phenomenon occurs at the upper end surface. In addition, such an abnormal surface (112
It was also found that 3) is due to an extremely fine flash generated on the end face during the molding of the light guide plate (1101).

In particular, in the above-mentioned surface light source device (1001), since only reflection / refraction is mainly used, a bright line is remarkably exhibited. As a countermeasure against this, as shown in FIG. 6, it is conceivable to dispose a light absorption layer (1133) on the main surface (1131) of the light guide plate (1101) where abnormal light first appears to prevent the occurrence of bright lines. However, this is not a preferable method because the non-effective light emitting region is increased.

Under these circumstances, the present invention has been achieved as a result of the sincere research conducted by the present inventor. Hereinafter, a surface light source device according to an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the surface light source device (1) of the first embodiment is a molded body made of acrylic resin and has a substantially rectangular shape having an effective light emitting area (111) of diagonal 10.4 inches. Light guide plate (101),
The first long end face (121a) of the light guide plate (101) is used as a light introduction surface, and the light source light from the tubular light source (501) and the tubular light source (501) arranged in proximity to the first long end face (121a) is efficiently provided. The reflective film (601) leading to the light guide plate (101), the first main surface (13) of the light guide plate (101)
1) It is configured by including a prism sheet (901) arranged above.

This light guide plate (101) has a first long end face (121a) having a thickness (t1) of 3 mm and a first long end face (121a), as shown in FIG. Second long end face opposite to
The thickness (t2) of (121b) is 1 mm, and it is formed in a wedge shape. A tubular light source is provided on the first main surface (131a) of the light guide plate (101).
It includes a plurality of comb-tooth-shaped prism protrusion rows (141) substantially parallel to the tube length direction of (501). This prism protrusion array (141) includes a first inclined surface (143) inclined in the vicinity of the tubular light source (501),
Including a second slope (145) intersecting with the first slope (143),
The first slope (143) intersects the first main surface (131a) of the light guide plate (101) at an angle (θ1), and the second slope (145) intersects the first main surface (131a) of the light guide plate (101). ) At an angle (θ2). Further, the pitch of the prism projection array (141) is gradually reduced as the distance from the tubular light source (501) is increased in order to make the brightness uniform.

The angle (θ1) formed by the first slope (143) and the first main surface (131) of the light guide plate (101) is set to, for example, 30 °, and the second slope (145) and the light guide plate (131). 101) first major surface
The angle (θ2) formed with (131a) is set to 90 ° in this embodiment. Here, the angle (θ1) is set to 30 °, but the angle (θ1) is not limited to this, and the light source that enters from the first long end face (121a) and propagates in the light guide plate (101) What is necessary is just to be set so as to reflect and guide the light to the second slope (145) of the prism projection row (141). However, if the angle (θ1) is too small, it becomes impossible to arrange a large number of projection rows (141), which may cause uneven brightness.
It is desirable to set within the range of 0 °. Further, here, the angle (θ2) is set to approximately 90 °, but is preferably 80 ° or more in order to reduce the spread of the emitted light.
An obtuse angle exceeding 90 ° may be used.

The light guide plate (101) has a tubular light source (5
The first long end face (121a) has the first and second main surfaces so that the light source light from (01) makes only the first long end face (121a) the light introduction surface.
The reflective film (601) is in contact with each of (131a) and (131b) by a line, and is in contact with the first and second main surfaces (131a) and (131b).

As described above, the light guide plate manufactured by a usual molding technique has a shape in which the first long end face and the first and second main surfaces are in contact with each other via an abnormal surface due to burrs or the like. Therefore, in this embodiment, the above-mentioned abnormal surface is
The first long end face (121a) is mirror-polished in a direction parallel to the long end face (121a), in a direction parallel to the first main surface (131a), and in a direction parallel to the second main surface (131b). Are the first and second main surfaces (131
It is made so as to make a line contact with each of a) and (131b).

The prism sheet (901) is substantially parallel to the prism protrusion array (141) of the light guide plate (101) and protrudes with respect to the light guide plate (101), and the prism protrusion array (141) of the light guide plate (101). A plurality of comb-teeth-shaped prism protrusion rows (911) formed with a sufficiently fine pitch.

Next, the operation of the surface light source device (1) will be described. The light source light emitted from the tubular light source (501) is propagated as light having a converging angle (Ω1) of about 42 ° in the light guide plate (101) due to the difference in refractive index between air and acrylic resin. Here, when the light source light propagating in the light guide plate (101) is guided to, for example, the first slope (143) of the prism projection row (141), the light source light is totally reflected by the first slope (143), The light is guided to the second inclined surface (145), which is the exit surface, and passes through the second inclined surface (145), and the condensing angle (Ω2) of approximately 90 ° with respect to the first main surface (131a) of the light guide plate (101). And is emitted from the light guide plate (101) as emitted light having directivity. Similarly, light guide plate (101)
Light source light propagated in, for example, a prism projection row (141)
When the light is guided to the second slope (145) of the light guide plate (101), the light is condensed at an angle of about 90 ° with respect to the first main surface (131a) of the light guide plate (101) through the second slope (145). The light is condensed and emitted from the light guide plate (101) as emitted light having directivity.

Thus, the first main surface of the light guide plate (101)
The light source light emitted from the (131a) is guided to the prism sheet (900), and the brightness peak thereof is emitted from the first main surface (1) of the light guide plate (101).
It is adjusted in the normal direction of 31a).

Thus, the surface light source device of the first embodiment
According to (1), since the linear light source is converted into a surface light source mainly by reflection and refraction, the utilization efficiency of the light source light is extremely high.
Further, since the light source light emitted from the surface light source device (1) has a directivity that is condensed, the first main surface of the light guide plate (101) is
An extremely high brightness can be secured in the normal direction of (131a), and it effectively works as a surface light source device for various applications.

Further, according to the surface light source device (1) of this embodiment, since only the first long end surface (121a) corresponding to the tubular light source (501) is used as the light introducing surface, abnormal light is guided by the light guide plate (101). ). Therefore, bright lines could be effectively prevented without increasing the ineffective light emitting region.

Next, referring to FIG. 3, regarding the surface light source device of the second embodiment of the present invention, the surface light source device of the first embodiment is different from the surface light source device of the first embodiment only. The same parts will be described with the same reference numerals.

In the surface light source device (1) of this embodiment, the first light guide plate (101) is arranged close to the tubular light source (501).
Long end face (121a), first major surface (131a) and first long end face (121a)
And a second taper surface (123b) arranged at the boundary between the first major surface (121a) and the first major surface (131b). It And, on the first taper surface (123a) and the second taper surface (123b),
Light absorbing black resin layers (125a) and (125b) are attached to cover the tapered surfaces (123a) and (123b), respectively. The reflective film (601) is arranged in contact with the first and second main surfaces (131a), (131b).

In this way, the light guide plate (101) is constructed so that the light source light from the tubular light source (501) uses only the first long end face (121a) as the light introduction face. As described above, the light guide plate manufactured by the normal molding technique has a shape in which the first long end face and the first and second main surfaces are in contact with each other through an abnormal surface due to burrs or the like. In the example, the abnormal surface is polished and removed in a taper shape having a desired angle with respect to the first long end surface (121a) to remove the first taper surface (1
23a) and the second taper surface (123b) are formed.

According to the surface light source device (1) of the second embodiment constructed as described above, since the linear light source is converted into the surface light source mainly by reflection and refraction, the utilization efficiency of the light source light is extremely high. . In addition, the light source light emitted from the surface light source device (1) has a directivity that is condensed, so that the light guide plate (10
It is possible to secure extremely high brightness in the normal direction of the first main surface (131a) of 1), and it works effectively as a surface light source device for various applications.

According to the surface light source device (1) of this embodiment, the first long end face (121a) also corresponds to the tubular light source (501).
Since only the light is introduced into the light guide plate, abnormal light will not enter
It is not incident inside. Therefore, bright lines could be effectively prevented without increasing the ineffective light emitting region.

In this embodiment, the tapered surfaces (123a), (123
b) black resin layer (125a), (1
Although 25b) is attached, a reflection sheet or the like may be used in order to improve the light utilization efficiency. However, the light guide plate
Since the light source light propagating in the (101) may be reflected undesirably, the tapered surfaces (123a) and (123b) have a light absorbing property, and the tubular light source (501) side has a reflective multi-layer sheet, respectively. You can also do it.

In all of the above-mentioned embodiments, the surface light source device including the prism projection array for controlling the outgoing light on the outgoing surface of the light guide plate has been described, but it may be on the back surface side or controlled by the groove or the like. It does not matter if it does. Further, the present invention works effectively even if the light guide plate is printed with a scattering pattern or the like.

[0039]

According to the present invention, it is possible to obtain a surface light source device capable of obtaining a surface light source having no unevenness in brightness and excellent in uniformity without the appearance of bright lines.

[Brief description of drawings]

FIG. 1 is a schematic front view of a surface light source device according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional perspective view of the surface light source device taken along the line AA ′ in FIG.

FIG. 3 is a schematic sectional perspective view of a surface light source device according to a second embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view of a conventional surface light source device.

FIG. 5 is a schematic cross-sectional view of a surface light source device for explaining the technical problem of the present invention.

FIG. 6 is a schematic cross-sectional view of a surface light source device of a comparative example.

[Explanation of symbols]

 (1) ... surface light source device (101) ... light guide plate (121a) ... first long end surface (121b) ... second long end surface (131a) ... first main surface (131b) ... second main surface (125a), ( 125b)… Black resin layer (501)… Tubular light source (901)… Prism sheet

Claims (5)

[Claims] 1. A light guide plate including a tubular light source, a light introduction surface for introducing light source light from the tubular light source, the light introduction surface being arranged in the vicinity of the tubular light source, and the light guide plate arranged on one main surface of the light guide plate. In a surface light source device having a control means for controlling the peak of the light source light expressed from, the light source light from the tubular light source has only one main surface corresponding to the tubular light source, the light introducing surface of the light guide plate. A surface light source device characterized by being incident as. 2. The one main surface of the light guide plate and the light introducing surface are substantially in line contact with each other.
The surface light source device as described in the above. 3. A light incidence blocking layer for blocking the introduction of the light source light into the light guide plate is disposed in a boundary region between the one main surface of the light guide plate and the light introduction surface. The surface light source device according to claim 1. 4. The light guide plate is arranged on the one main surface of the light guide plate so as to selectively emit the light source light propagating in the light guide plate from the one main surface side of the light guide plate. The surface light source device according to claim 1, comprising a plurality of protrusions. 5. The control means controls the peak of the light source light selectively emitted from the one main surface of the light guide plate in a direction normal to the one main surface. The surface light source device described.